Electrical switch



Oct. 10, 1944. PRAVDA ELECTRICAL swlwcn Filed May 10,' 1943 2 Sheets-Sheet 1 INVENTOR. /Y/4 7011/ f. P/F/IVDI Oct. 10, 1944. M, PRAVDA 2,360,072

ELECTRICAL SWITCH Filed May 10, 1943 2 Sheets-Sheet 2 Patented Oct. 10, 1944 ELECTRICAL SWITCH Milton F. Pravda, Bediord, Ohio, assignor, by mesne assignments, to Jack & Heintz, Inc., Cleveland, Ohio, a corporation of Ohio Application May 10, 1943, Serial No. 486,279

4 Claims.

This invention relates in general to an improvement in electrical switches and more particularly to an improvement in snap action switches.

Often it becomes desirable to control the voltage and current in various types of circuits by having a snap action switch to change the arrangement of the circuits by closing some lines and opening others. For example, an application of the snap action switch may be the changing of the field connections in an electric motor, where it is desirable to have speed of the rotor varied in steps from zero R. P. M. to full rated R. P. M. In such a motor application a full stop of the switching gear should be effected in each switching position prior to proceeding to the next position to prevent the large surge currents, which would occur if the motor. switch were actuated directly from an off to a full on position, from entering the motors field coils.

Therefore, it is the primary object of this invention to provide a snap switch with an off position and a plurality of on positions in which it will be impossible to switch the contactors from one step through an intermediate step to a third step without coming to a complete rest in the intermediate position, when the contactors are being moved from the off position to the full on position.

With the foregoing and other objects in view, the invention resides in the combination of parts and in the details of construction and operation hereinafter set forth in the following specification and appended claims, certain embodiments thereof being illustrated in the accompanying drawings in which:

Figure l is a diagrammatic view of the stationary and sliding contacts of snap switch, the stationary contacts being connected to a field coil of a motor for illustrative purposes.

Figure 2 is a view in side elevation of a snapv action switch in its off position, mounted in an insulating housing.

Figure 3 is a diagrammatic view of the stationary and the sliding contacts with the sliding contacts in the off position of the switch similar to Figure 2.

Figure 4 is a view in side elevation of the switch as it arrives in its intermediate or low position from its off position.

Figure 5 is a diagrammatic view of the stationary and the sliding contacts with the sliding contacts in the intermediate or low position similar to Figure 4.

Figure .6 is a view in side elevation of the switch in its full on position having its sliding contactors in the position shown in Figure. 1.

Figure 7 is a view in side elevation of the switch resting in its intermediate position with its sliding contacts in the position shown by Figure 5.

Figure 8 is a top plan view of the switch, similar to Figure '7, less the insulating housing.

Referring more particularly to the drawings, the switch mechanism is carried by a frame I contained within an insulated housing 2 which also contains stationary contacts 35 and 6-8 and sliding contact jumpers 9 and Ill. The frame I is provided with indexing notches II, I2 and I3 in which a pin II, which carries the sliding contact jumpers, reposes when in the full on, intermediate and off positions respectively. Figures 1, 3 and 5 show the sliding contact jumpersdiagrammatically in positions corresponding to the position of pin it in each of the notches I3, I2

and II. A practical circuit application of the switch is shown in Figure 1 in which field coils 29, 30, 3| and 32 of motor 33 are changed from a series connection as would be had when the sliding contactors are as shown in Figure 5, the low position, to a series parallel connection when the sliding contactors are in the position shown by Figure 1.

In operation the sliding contact jumpers, which are insulated from each other, are moved in unison from one stationary contact step to the next by the pin I4 under the control of a lever I5. Lever I5, which moves about a pivot I6 has an insulating body II with a cam plate I8 opposedly mounted thereon with respect to the lever I5. Also mounted on the pivot I6 is a yoke I9 and a spring 20 which connects the yoke with the lever I5.

When the lever I5 is moved from the ofi position Figure 1 toward the intermediate position Figure 4, the cam plate I8 lifts the pin I4 out of notch I3 against the action of a spring M which is mounted in the upper part of the yoke. The pin II at the same time forces upward an L shaped lever 22, which is pivoted on a pin 23'. In this upward motion the L portion 24 of the lever 22 contacts a flexible tailpiece 25, which is mounted on the surface of an indexing stop 26, and moves it upward, consequently forcing the stop 26 downward about pivot 21 and against the positive spring action of a flexible metal spring 28 which is mounted on the frame I.

As the pin I4 clears the edge of notch I3, yoke I9, which is normally in degree alignment with lever I5, is snapped over to the intermediate position by the action of spring 20, where its movement toward the full on position is halted by the indexing stop 26. With the upperportion of the yoke in contact with the stop it is impossible to move the sliding contact jumpers into the full on position thus preventing the possibility of skipping the intermediate step in going from the off to the full on position.

In order to move the sliding contact jumpers to the full on position, the pressure exerted on the lever IE to move it from the off to the intermediate position must be removed momentarily in order to permit the stop 26 to be moved into its normal position by the action of spring 28 as the lever 22 moves downward about its pivot. Upon resumption of manual pressure on lever IS the pin I4 is lifted from its position in notch 12 by the action of cam 18. The upper surface of the yoke moves far enough toward the full on position to avoid re-engagement with the indexing stop, the extremity of the stop merely passing along the upper surface of the yoke, and the pin I4 is snapped over into notch II. The snap action which occurs in this step from the intermediate to the full on position is accomplished ina manner similar to the action from the ofi to intermediate position.

In returning the sliding contact Jumpers to the off position from the full on position, the lever I5 may be moved to the intermediate position or may under continued pressure be moved through the intermediate position to the off position without stopping if so desired. A positive stop in the intermediate position on the return of the lever to the of! position may be obtained by installing an indexing stop mechanism similar to the arrangement already described on the opposite end of the switch frame.

I claim:

1, An electrical switch having a plurality of sets of stationary contacts and a pair of sliding contacts, snap action means for moving said sliding contacts from engagement with one set of stationary contacts to the next in either direction through a series of steps, a positive stop indexing mechanism, and means responsive to said snap action means for moving said indexing mechanism into a position where it is adapted to positively stop the forward movement of said snap action means at a predetermined step.

2. An electrical switch comprising a plurality of sets of stationary contacts and a pair of sliding contacts, a manually operated sna/p action switching mechanism, a frame for holding said contacts and said switching mechanism and a positive stop indexing mechanism mounted on said frame so that it is moved simultaneously with the movement of the manually operated snap action switching mechanism in such a manner as to stop the movement of the sliding contact controlling snap action switching mechaziisg at a predetermined set of stationary con- 3. In an electrical switch having a plurality of sets of stationary contacts and a pair of sliding contacts, a snap action switching mechanism for moving said sliding contacts, a positive stop indexing mechanism, means responsive to manual pressure exerted on said switching mechanism for moving said sliding contacts from engagement with one set of stationary contacts to the next, means responsive to the movement of the switching mechanism for causing said indexing mechanism to be forced into engagement with said switching mechanism so as to stop movement of said mechanism at a predetermined step, means responsive to the release of the pressure exerted on said switching mechanism for causing said indexing mechanism to become disengaged from said switching mechanism, and means responsive to renewal of pressure on the switching mechanism to cause further snap action movement of said mechanism in the same direction to the next set of contacts without re-engagement with said indexing mechanism.

4. In an electrical switch having a plurality of stationary contacts and a pair of sliding contacts, a positive stop indexing mechanism, a snap action switching mechanism including an operating lever and a plate, having a cam surface, rigidly connected to the operating lever, a frame for carrying the stationary and sliding contacts, the indexing mechanism and the snap action switching mechanism, a lever, having a cam surface, pivoted at. one end to the frame and having its free end extending to a position adjacent to the indexing stop mechanism, means responsive to movement of the cam in the snap action switching mechanism, as said mechanism is moved from one step to the next, for moving the pivoted lever, means responsive to movement of said lever for forcing the indexing mechanism into engagement with the switching mechanism to stop the movement of said mechanism at a predetermined set of stationary contacts, resilient means, following th release of pressure on the operating lever, for causing the indexing mechanism to disengage the switching mechanism, and means responsive to renewal of pressure on th operating lever to cause further snap action movement of the switching mechanism in the same direction to the next set of stationary contacts without re-engagement with the indexing mechanism.

MILTON F. PRAVDA. 

